Study of a hollow laser beam for cladding

Laser cladding, as a promising manufacturing technology, has been widely used in industry for component recovery and surface modification. In this paper, a hollow laser beam was proposed to optimize the laser intensity distribution. A three-dimensional (3-D) finite element (FE) model was developed using ANSYS to investigate the thermal field in the clad deposited by a hollow laser beam. The thermal results, such as the temperature distribution and the cooling rate, were investigated. The effect of the hollow ratio between the inner and outer radius of the hollow beam on the molten pool shape was also studied. The temperature at the boundary of the molten pool was higher than at the center. A clad with a flat metallurgical bonding was formed. The microstructure in the clad was mainly consisted of fine dendrites except the large columnar structures along the bonding. The hardness distribution of the clad was associated with the grain size distribution and the dilution by the substrate. The molten pool was not able to be generated with a high hollow ratio, while overheated at the center with a low hollow ratio. Based on the comparison with the Gaussian laser beam, the hollow laser beam could effectively alleviate the overheating at the center of the clad.